1. Field of the Invention
This invention relates to a wound golf ball having a multilayer cover, and more particularly, to a wound golf ball which is improved in restitution, spin, and durability.
2. Prior Art
As is well known in the art, wound golf balls are superior in spin, controllability, and hitting feel compared to solid golf balls.
In the prior art, wound golf balls are manufactured by winding high stretching thread rubber around a liquid or solid center to form a thread rubber layer thereon, and enclosing the thread rubber layer with a cover of balata rubber or ionomer resin.
As compared with wound balata balls, the wound golf balls using ionomer resins as the cover stock are superior in flight distance on driver shots, but inferior in spin properties necessary for approach play on the green. On the other hand, wound balata balls are less durable, for example, in that their cover presenting the ball surface can be scuffed or fretted by bunker shots and cut when topped with iron clubs.
For the purpose of improving spin property and durability, a wound golf ball using a softer ionomer resin as the cover stock was also proposed. This ball has problems that it produces little difference in flight distance on driver shots from the wound balata balls and that it can be cut in the cover when topped with iron clubs as are the wound balata balls.
From this standpoint, the inventors proposed in JP-A 224323/1996 a new type of wound golf ball comprising a solid center and a cover of a two layer structure wherein the cover outer layer has a low hardness and the cover inner layer has a high hardness. This wound golf ball has many advantages. On approach shots, the ball is susceptible to spin and hence, improved in spin properties and controllability because the cover outer layer is soft. Because the cover inner layer has a high hardness and the cover as a whole has satisfactory restitution or resilience, the ball produces an increased initial velocity and a low spin rate on driver shots, which insures an increased flight distance. The combination of the soft outer layer and the hard inner layer provides improved cut durability. The outer layer formed of a low hardness ionomer resin is improved in scuff resistance over a balata cover and high hardness ionomer resin covers.
Such wound golf balls, however, are still desired to increase the ball bounce for increasing the flight distance and to further improve the spin performance. The balls are also desired to be so durable that the ball can be used repeated times.